OUR FACE FROM FISH TO MAN 



amphibians air may either be gulped in through 

 the mouth or sucked in through the nose, which 

 thus functions in breathing as well as in smelling. 



By the time we reach the mammal-like reptiles 

 of the Triassic of South Africa (Fig. 53VI) we find 

 the paired olfactory capsules greatly elongated in a 

 fore-and-aft direction, and in the highest members 

 of this series, as shown by iron-stone casts of the 

 interior of the nasal chamber, the median bony 

 partition now supported scroll-like outgrowths 

 like the delicate turbinate bones of mammals 

 (Watson). The delicate olfactory membrane thus 

 spread out on these scrolls, which in many mam- 

 mals become complicated with secondary scrolls, 

 thus secures a wide surface for testing the odors 

 of the air drawn in. 



In the living amphibians, reptiles and more 

 primitive mammals there is also a pair of small 

 cartilaginous scrolls near the bottom of the 

 median cartilaginous partition, which contains a 

 folded pocket of the olfactory membrane; from this 

 pocket a very fine tube leads downward, opening 

 into the cavity of the mouth. This whole arrange- 

 ment is called Jacobson's organ. Primitively 



Jacobson's organ seems to have served for the 



158 



